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Structure ofRNi3Al9(R= Y, Gd, Dy, Er) with either ordered or partly disordered arrangement of Al-atom triangles and rare-earth-metal atoms

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Published in Acta Crystallographica. B, Structural Science. 1993, vol. 49, no. 3, p. 468-474
Abstract ErNi<sub>3</sub>A1<sub>9</sub>, M<sub>r</sub> = 586.22, trigonal, new type, hR78, R32 - f<sup>2</sup>edc<sup>4</sup> (No. 155), a = 7.2716 (5), c=27.346 (3) A, V = 1252.2 (2)A<sup>3</sup>, Z = 6, D<sub>x</sub> = 4.664 Mg m <sup>-3</sup>, A(Mo Ka) = 0.71073/k, u = 17.654 mm<sup>-1</sup>, F(000) = 1614, T = 293 K, wR = 0.021 for 785 contributing unique reflections. The structure is built up of three kinds of monoatomic layer perpendicular to c: Al-atom layers with triangular mesh, Ni-atom layers with triangular mesh and layers containing two rare-earth-metal atoms for one Al-atom triangle. GdNi<sub>3</sub>A1<sub>9</sub> [a = 7.3006 (9), c = 27.478 (5)/A, wR = 0.020 for 791 reflections] is isotypic. YNi<sub>3</sub>AI<sub>9</sub> [a = 7.2894 (7), c = 27.430 (5) A, wR =0.035 for 635 reflections] and DyNi<sub>3</sub>AI<sub>9</sub> [a = 7.2723 (9), c = 27.344 (6)A, wR = 0.027 for 682 reflections] crystallize in related structures with a partly disordered arrangement of Al-atom triangles and rare-earth-metal atoms. Similar monoatomic layers to those in ErNi<sub>3</sub>AI<sub>9</sub> build up the orthorhombic structure of Y<sub>2</sub>Co<sub>3</sub>AI<sub>9</sub> (Y<sub>2</sub>Co<sub>3</sub>Ga<sub>9</sub> type). The stoichiometry 1:3:9 is related to that of RzT3A19 by replacing every second mixed layer of composition R<sub>2</sub>AI<sub>3</sub> by an Al-atom layer (A1<sub>3</sub>): 6RT<sub>3</sub>A1<sub>9</sub> = 6R<sub>2</sub>T<sub>3</sub>AI<sub>9</sub> - 3R<sub>2</sub>AI<sub>3</sub> + 3A1<sub>3</sub>.
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GLADYSHEVSKII, Roman et al. Structure ofRNi3Al9(R= Y, Gd, Dy, Er) with either ordered or partly disordered arrangement of Al-atom triangles and rare-earth-metal atoms. In: Acta Crystallographica. B, Structural Science, 1993, vol. 49, n° 3, p. 468-474. https://archive-ouverte.unige.ch/unige:81164

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